Auxiliary sender circuit



16 Sheets-Sheet 1 Jan. 6, 1959 c. o. PARKS AuxxLIARY sENDER CIRCUIT Filed July 15, 1956 ATTORNEY Jan. 6, 1959 c. o. PARKS AUXILIARY SENDER CIRCUIT Filed July l5.v 1956 16 Sheets-Sheet 2 NGN.

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AUXILIARY SENDER CIRC'UIT Filed July 13, 1956 16 SheQt-Sheeb 5 Pc/ PU/ s/NG a CONTROL /NVENTOR C. O. PA R/(S ATTORNEY Jan. 6, 1959 c. o. PARKS 2,867,690

AUXILIARY sENDER CIRCUT i.

Filed July 13, 1956 16 Sheets-Sheet 4 N O N MA RKER CONNECTOR MA RKER A TTORNE V Flc. 4

Jan. 6, 1959 c. o. PARKS AUXILI'ARY SENDER CIRCUIT Filed July 13, 1956 16 Sheets-Sheet 5 /NVE/VTOR By C. 0. PAR/(5 ATTORNEY Jan. 6, 1959 c. o. PARKS AUXILIARY SENDER CIRCUIT 16 Sheets-Sheet 6 Filed July 13, 1956 /NVENTOR I BV C. O. PAR/(5 ATTORNEY Jan. 6, 1959 c. o. PARKS AUXILIARY SENDER CIRCUIT 16 Sheets-Sheet 7 Filed July 13, 1956 NGN /NVE N TUR BVC. o. PAR/fs C. hlm

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By c. o. PAR/fs diaz@- MGM ATTORNEY C. O. PARKS AUXILIARY SENDER CIRCUIT Jan. 6, 195.9

Filed July 13, 1956 Jn. 6, 1959 c. o. PARKS 2,867,590

UXILIRY SENDER CIRCUIT Filed July 13, 195e 1e sheets-sheet 11 By C.

ATTORNEY FIG. l/

Jan. 6, 1959 c. o. PARKS AUXILIARY SENDER CIRCUT Filed July 13, 1956 16 Sheets-Sheet 12 @Gmb ATTORNEY AUXILIARY SENDER CIRCUIT Jan. 6, 1959 16 Sheets-Sheet 15 Filed July l5, 1956 /Nl/ENTOR u C. 0. PAR/(S BV C, han@ ATTORNEY Jan. 6, 1959 c. o. PARKS AUXILIARY SENDER CIRCUIT 16 Sheets-Sheet 14 Filed July 13, 1956 /A/VE/VTOR BV C.O. PARKS ATTORNEY Jan. 6, 1959 co. PARKS AUXILIARY SENDER CIRCUIT 16 Sheets-Sheet 15 Filed July 13. 1956 /A/ VEA/TOR C. 0. PAR/(5 d, )km

ATTORNEY Jan. 6, 1959 c. o. PARKS 2,867,690

AUXILIARY SENDER CIRCUIT Filed July 1s, 195e 1e sheets-sheet 16 MULT/ FREQUENCY GENERATOR /NI/ENTOR Q y CO. PAR/(5 k) e. @am

A TTORNEV AUXILIARY SENDER CIRCUIT Charles 0. Parks, East Norwalk, Conn., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 13, 1956, Serial No. 597,746

11 Claims. (Cl. 179-18).

This -invention relates to telephone systems andhas as its 'object to increase in scope the service provided by local dial telephone systems. l

More particularly, the present invention provides means for readily modifying dial telephone oices, designed to establish onlylocal calls, so that they can handle customer Adialed toll'calls, now generally termed direct distance dialing. As an auxiliary function, the present invention also providesmeans for giving such offices direct access to other local oices requiring the use of multi-frequency *marker and passes these three digits to the marker. The

marker translates these digits into a routing indication from which it derives information which it uses in selecting an idle trunk leading to the identified office and in connecting the selected trunk with the district junctor t'o which the calling line has been extended. At the same time, it derives information required by the sender such as class of the call, etc. which it passes back to the sender, followed by a release signal. From the class of call indication the sender determines the type of outpulsing to be used in controlling the called office, sets up the required type of control circuit passing by way of the district junctor and the selected outgoing trunk to the distant oice and prepares the proper pulsing equipment. This control circuit, which is used both for testing the` condition of the trunk and for transmitting the designation to the distant office,V is usu`ally called the fundamental circuit.

.sender is provided which'is or is not inserted' in the fundaymental circuit in accordance with the designation of the called office.

A further feature of the invention relates to means for connecting the auxiliary sender with the subscriber sender either in accordance with the value of a particular digit or in accordancev with a determination made by themarker from a translation of aplurality of digits.

According to an additional feature of the invention, the auxiliary sender is set by pulses transmitted in one code by the subscriber sender over a portion of the fundamental circuit and transmits the recorded designation to the. distant office in accordance with a different code over a different portion of the fundamental circuit.

Furthermore, means is provided in the auxiliary sender to receive and register digits according to two codes together with means operated in accordance with the identty of the oice to which the call is directed to determine whether' one or both of said receiving means shall be used.

K 2,867,690 Patented Jan. 6,

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Means for generating the pulses of the different` code is normally under the control of one of thesaid receiving means but is automatically controlled if said other receiv- 'ing means is also used.

scriber sender;

Fig. 3 shows a part of the crossbar registerof a. Subscriber sender;

Fig. 3 shows a part scriber sender; f 1 t Fig. 4 shows in diagrammatic form a marker connector of the control equipment of a` sub- `and a marker together with circuits by whichthe subscriber sen-der controls the marker connector;

Fig. 5 shows that part of the subscriber sender, which controls the connection with the auxiliary sender;

Figs. 6 and 7 show the auxiliary sender connector; Figs. 8 and 9 show control circuits for the auxiliary sender cponnector;

Figs. 10 to 16 show the auxiliary sender, Fig. 1,0 showing the code pulse receiving relays, Fig. 11 showing trunk test relays and the dial pulse receiving relay, Fig. 12 showing the dial pulse counting relays, Fig. 13 showing the out-pulse generator relays, Figs. 14 and 15 showing two digit registers and the steering relays, and Fig. 16 showing the multifrequency out-pulsing control; Fig. 17 shows the manner in which Figs. 1 to 16 shoul be arranged. The circuits of Figs. l to 4 have been taken from th disclosure of Patent 2,235,803 granted to W. W. Carpenter March 18, 1941, and that patent is hereby incorporated by reference in the present disclosure. For convenience in consulting the Carpenter patent, although functional designations have been shown and will be employed in describing the operations in connection with the present invention, the numerical designations employed in the Carpenter patent have also been shown. Functional designation for relays, etc. will be employed in the present description, with an indication of the figure in which the ap paratus appears given by appending to the functional designation the figure number enclosed in parentheses.

Brief description link 103 to the pulsing relay L(1) of an idle l'subscriber sender. The, subscribersender includes a crossbarltype -register which hasone hundred crosspoints arranged in ten vertical groups corresponding to the ten digits from 0 through 9 and ten horizontal levels. A crosspoint in the first level is operated to register the identity of the frame on which the district junctor is located. The first 'or A digit of the called line designation is shown as registered by operating corresponding crosspoints in the next two levels, to agree with the showing of the aboveidentified Carpenter patent. The B and C office code digits and the thousands, hundreds, tens, and units digits of the line number are registered on the fourth to ninth levels of the switch. If a five digit line number or aline number having a party line designation is dialed, the fifth digit or the party letter will be registered'von th tenth level. 1

In registering the designation of a wanted subscriber, relay 1.(1) responds to the operation of the calling sul scribers dial, in turn operating the pulse divider 101 and the counting relays 102. At the end of each digithn of the select magnets SELO(2) to SEL9(2), corresponding to the value of the digit dialed, is operated under the control of the counting relays 102 to prepare the corresponding vertical of the register switch. The operated select magnet causes a cycle of operation which results vin the operation of one of the hold magnets HMA(2) to .proper level.

When the third or C digit has been registered, the marker connector 401 is operated to select an idle marker such as marker 402 and connect Vthat marker with the sender. frame identity, are transmitted to the marker, vwhich translates these digits into two sets of routing information. One set of information is employed by the marker itself for selecting an idle trunk outgoing to the identified office and setting up a connection between the district junctor, with which the calling line has been connected, and the selected outgoing trunk. The other set of information includes information required by the sender for completing its operation. This information, which is returned to the sender, tells the sender the type of pulsing required by the identified office, for example, revertive pulsing or PCI code pulsing, the resistance of the selected trunk, the number of digits to be out-pulsed, the number of digits to be expected from the calling subscriber, etc. When this information has been transmitted to the sender and the marker has completed its functions the marker connector and the marker is released.

When the marker has released, the sender sets up a trunk test circuit and, if the result of the trunk test indicates that the distant ofiice is ready to be operated, transfers the trunk test circuit to the fundamental circuit by which the sender may control the distant oiice. The sender is normally arranged to receive revertive pulses from a panel or crossbar oiiice or to transmit PCI pulses to manual ofces equipped with call indicators. When the sender has completed its function, relay 2501 in the district junctor is operated to complete the talking circuit between the calling line and the distant oflice and the sender releases.

To adapt the subscriber sender above described for direct distance dialing, auxiliary senders are provided, together with a connector for associating an auxiliary sender with the subscriber sender. The subscriber sender is informed that an auxiliary sender will be required by the revistration on the second or B register of the digit or the digit 1 which identifies an area code and, therefore, indicates that a l0-digit number is being dialed. When the seventh .digit has been registered, the auxiliary sender connector is operated to connect the subscriber sender with the auxiliary sender, and, as soon as the eighth vdigit has been registered, the pulsing circuit is transferred to the auxiliary sender where the ninth and tenth digits are registered on the tens digit Aregister T(l4) and the units register U() of the auxiliary sender.

The marker is called in in the normal manner but Areceives the area code rather than the office code. In translating the area code, the marker recognizes that an auxiliary sender will be required and, therefore, sets the class relays of the subscriber sender for PCI'code pulsing.

With the auxiliary sender attached to the subscriber fsender, the trunk test circuit is switched through to the 'auxiliary sender so that the trunk test circuit of the vsubscrlber sender terminates in the auxiliary sender and the auxiliary sender establishes the trunk test circuit to the distant oice. The auxiliary sender recognizes 'the ready The lirst three digits, as well as the district 4 or assignment indication by the distant oiiice and relays this'information to the subscriber sender.

When the auxiliary sender relays the assignment signal to the subscriber sender, the subscriber sender pulses the eight digits registered therein to the auxiliary sender by means of PCI code pulses. In the auxiliary sender these digits are alternately registered on odd register O( 16) and even register E( 16). While the second digit is 'being registered on the register E(16), the auxiliary sender transmits the digit registered on register O( 16) to the distant oiice in the form of multifrequency code pulses, after which the odd register is released to receive the third digit. While the third digit is being registered, the second digit is transmitted. Following the registration and transmission of the eighth digit, the ninth and tenth digits, which are registered directly in the auxiliary sender are transmitted. A set of steering relays in the auxiliary sender controls the overlapping operation of receiving digits from the subscriber sender and transmitting digits to the distant oiiice.

The auxiliary sender also permits the oice at which it is located to have access to other local offices which require multifrequency pulsing. In this case, the subscriber sender is instructed to call in an auxiliary sender by a special class indication from the marker. Under this condition, all of the dialed digits are registered in the subscriber sender and pulsing terminates when the last digit has been received and transmitted by the auxiliary sender.

Since the auxiliary sender is set by PCI code pulses, only the trunk test circuit and the PCI fundamental circuit have been shown in the subscriber sender. Similarly, since the only digits having special significance in the use of the auxiliary sender are the B digit, the units digit, and the stations digit, the registers for storing these digits have been shown and the remaining registers have been merely indicated.

Detailed description-LocalPCl call Assuming that the subscriber at station 1000 wishes to make a local call to a subscriber at the call indicator oce CI(1), the removal of the receiver from the switchhook causes his line to be extended through line switches PLS(1) and SLS(1) to conductors 2549 and 2550 which are further extended by the sender link to conductors l2450 and 2451. The operation of the line switch and the sender link takes place as completely described in the above-identified Carpenter patent. In the subscriber sender conductor 2451 is extended to conductor 3019, front contact of off-normal relay ON1(1), back contact of advance relay AV4(1), middle winding of pulsing relay L(1) to battery, while conductor 2450 is extended to conductor 3020, front contact of relay ON1(1), and back contact of relay AV4(l-) to ground. Since conductors 3019 and 3020 are connected together at substation 1000, `rela-y L(1) operates, closing a circuit from ground over a back contact of relay lS/1(3), conductor 3615, front contact of relay L(1) to battery through the winding of SR(1). Relay SR(1) is slow to release and prepares the circuit for recording the digits `dialed by the subscriber at substation 1000. When the subscriber operates his dial, relay L(1) releases at each interruption of its circuit by the dial and completes .a circuit lfrom ground on conductor 3615, back contact of relay L( l), conductor 100, contact 8 of relay DPT(5), conductor` 500, front contact of relay SRU), conductor 3610, back contact of relay STL( l), and conductor 3619 to the pulse divider 101, which in turn alternately grounds conductors 3035 and 3620 to operate the counting relays 102. Conductor 3620 extends over contact 9 of relay DPT(5) to conductor 3039 leading to -the counting relay circuit 102. At the end of the digit the counting relays operate one of the-select magnets SELO(2), SEL1(2), SEL9(2) .to prepare the crossbar register for operation. The operated magnet yextends its operating ground to .conductor 3427 winding of relay Sli/11(2). Relay SM1(2)Hoperates and closes an obvious circuit thron gh the left winding of relay SM2(2) operating the latter relay. Relay SM2(2) in turn operates relay SM3(2). Relay SM3(2) opens the operating circuit for relay SM1(2) but closes a holding circuit for relay SM2(2) through the right winding of the relay under the control of the hold magnet sequence circuit 204. The hold magnet sequence circuit advances as each digit is registered to provide an operating circuit for the proper one of the hold magnets HMA(2) to HMSTA(2). When the hold magnet is operated, relay SM2(2) releases, in turn releasing relay SM3(2) to pre pare for the registration of the next digit and to control the operation of the hold magnet individual to the digit whereby the digit dialed is set up on the corresponding crosspoint of the proper level of the register. The operation of the pulse divider, counting relays, the select magnets and hold magnets all takes place as described in detail in the'above-identied Carpenter patent. For convenience, the levels which constitute the frame register, the A digit register, and its auxiliary A register and the C digit register, the thousands register, hundreds register and tens register have been indicated merely by boxes. When the third, or C digit has been registered and the hold magnet HMC(2) operates, an auxiliary relay CL(2) is operated which connects ground to conductor 3118 completing a circuit over back contacts of relay TR1(4) and TR3(4) to battery through the winding of relay DST(4).

Relay DST(4) connects battery to conductor 3124 and over a back contact of relay DRL(4) to conductor 3132 leading to the marker connector which selects and connects an idle marker with the sender. The rst three digits are then transferred to the marker which translates these three digits into route information by which it selects a trunk outgoing to oflice CI(l) and operates switches such as switches DPS(l), DSS(1), OPS(1) and OSS(l) to prepare a connection between the calling line and the called oiiice. In addition, the marker determines the nature of the called oice and sets up a class indication in the sender to control the further operation of the sender. Since it was assumed that the call was directed to call indicator ofce Cl(1), class relays CL1(4), CL2(3), and CL4(3) are operated. When the marker has completed its functions it operates relay DRL(4) which results in the-operation of relays 86(3) and S6(3). Relay DRL(4) disconects battery from the marker connector, causing the marker connector and the marker to release.

With relay S6'(3) operated, a trunk test circuit is established from the tip of the outgoing trunk through the oice and district switches to conductor 2552 which extends through the sender link to conductor 2452, contacts 12 and 10 of relay SWF(5), conductor 501, through compensating resistances Z1(3) and 22(3) controlled by relays CR3(3) and CR4(3), which are also set by the marker, conductor 3537, front contact of relay S6'(3), front contact of relay CL4(3), back contact of relay CI2(3) through the winding of relay TG( 3), inner upper back contact of relay FS1(3), lower winding of relay OF(3), back contact of relay AV2(3), conductor 300, contacts 6 and 8 of relay SWF(5), conductor 2543, through the sender link to conductor 2553, and through the district and oice switches to the ring conductor of the trunk. Assuming that the trunk is in satisfactory condition, relay TG(3) will operate, in turn operating relays TG1(3) and TG2(3). Relay TG2(3), in operating, Closes a circuit from ground over its contact 4, over front contacts of relays 86(3) and CL4(3), back contact of relay OF1(3), and front contact of relay CL2( 3) to battery through the winding of relay Cl1(3). Relay CI1(3) operates and closes a locking circuit for itself over the front contact of relay CL2(3), back contact of -relay 0F1(3), front contact of relay CI1(3) vandconductor 3615 toground at the back contact` of vrelay -AV1(3). Relay CI1(3), inl turn, operates relay C12-3).

When the operator or sender is ready to receivethe .called number, the circuit above traced is openedand relay TG(3) releases, in turn releasing relays VTG1(3) and TG2(3). With relay TG2(3) released, the out-pulsing circuit extends from conductor 2452 as above traced `to conductor 3537, contact 4 of relay CI(3), back contact 1 of relay TG2(3) to the PCI pulsing and control circuit 301 and from conductor 2453 as above traced to conductor 300, back contact of relay AV2(3), contact 3 of relay CI1(3), and contact 3 of relay TG2(3) to the PCI pulsing and control circuit 301. The designation of the called subscriber, as registered in the crossbar register, is now transmitted to the distant ofce. When out-pulsing has been completed, relay AV1(3) s operated and th subscriber sender restored to normal. t

Seizure of auxiliary sender IO-dgt toll call *l As previously mentioned, the auxiliary sender is required either for completing ten-digit toll calls or where the local called oice requires multifrequency pulsing.

Ten-digit toll calls are identied by an area code in which the second digit is either 0 or 1. When such a code is registered in the subscriber sender, either crosspoint 3230 or 3231 is operated. These crosspoints represent the digits 0 or l in the register which normally registers the second or B ofce digit. With either crosspoint 3230 or 3231 closed, a circuit is completed from ground overa back contact of relay DRL(4), conductor 400,

contact of crosspoint 3230 or 3231, conductor 200, contact 1 of relay DPT(5), contact 2 of relay SA(5), and contact 6 and winding of relay AS(5) to olf-normal battery. Relay AS(5) operates in this circuit and locks to ground over its contact 7. When the seventh digit of the designation has been registered, a circuit is completed from ground over a contact of any one of the operated crosspoints 3330 to 3339 of the units register to conductor 201, contact 11 of relay AS(5) and conductor 502 to the start circuit of the auxiliary Sender link.

In the case of calls requiring multifrequency outpulsing, the called line designation is registered in the usual manner and the marker indicates thatv multifrequency pulsing is required by operating relay 7DG(5) which locks over its contact 4 and conductor 503 to ground over front contacts of relays DST(4) and DRL(4) when the marker releases. With relay 7DG(5) operated, a circuit is closed from ground over contact 5 of relay 7DG(5), contact 1 of relay DPT(5), contact 2 of relay vSA(5), contact 6 and winding of relay AS(5) to oinormal battery operating relay AS(5). The registration of a digit on the units register is effective as above described to connect ground to the start conductor for the auxiliary sender connector.

- The purpose of waiting to close the start circuit for the auxiliary sender link until the seventh digit has been received is both to save on the holding time of the auxiliary sender and thereby reduce the number of auxiliary senders required and to prevent calling in the auxiliary sender when service codes, such as 211, 411, etc., are dialed. Since for a l-digit call there is only a limited time available during'which to seize the auxiliary sender a particularly fast acting link circuit is provided.,v

The sender link frame comprises ten crossbar switch units whereby any one of one hundred subscriber senders quired to connect the subscriber sender with an auxiliary sender, in practice each crossbar switch unitl would .comprise the equivalent of; twoten-.point switches ,w h ich are operated in parallel, with half of the Eleadsnextend` 7 ing `through one switch land the other half ofthe leads extending through the other switch.

,Controlof the link switches is laccomplished by means of a series of chain circuits providing apreierence and lockout between the subscriber senders appearing in the same switch and a-preference 'rand 'lockout between the -switches so that only one subscriber sender can be connected to an auxiliary sender at a time. The auxiliary senders lare also arranged in a preference chain to which the group of subscriber senders have `access at different i( points so as .to .equalize the wear on the auxiliary senders. If there are enough subscriber senders to require more than one sender link frame, as many connections can be set up simultaneously as `there are frames, As soon as one subscriber lsender has been connected to an auxiliary sender, another subscriber sender can be connected to another auxiliary sender through the same frame. As many coincident connections can exist as there are auxiliary senders.

With ground vconnected to conductor 502, a circuit is ycompleted vover a back Ycontact of holdmagnet H(6), conductor 600, Winding and contact'9 of relay STO(8), which is individual to the sender of Figs. l to 5, and conductor 801 to battery over back contact of gating relay GA(9). Relay STO(8) operates in this circuit and locks to battery over its own contact l0. At its contact 13, relay STO(8) disconnects battery from the windings of other start relays individual to other subscriber senders appearing in the same switch. At its contact 11, relay STO(8) connects ground to conductor 802, operating the gating relay GA(9) to prevent the later operation of any other start relay in the same or any other group. If no other subscriber sender is attempting to connect with an auxiliary sender at this time, all of the preference relays APO(7) to AP9(7) individual to the auxiliary senders will be released, and a circuit is closed from vbattery through the Winding of group relay GMS), contact 12 of 'relay STO(8), conductor 503, over the back contacts of intermediate .group relays (not shown), back contact of group relay G9(9), conductor 900 over the back contacts of relays AP9(7) to APO(7) to ground. Group relay G(8) operates in this circuit and locks over its contact 4, contact 2 of relay STO(8) and conductor 604 to ground at the back contact of hold magnet H0(6) which is individual to the subscriber sender. Group relay G0(S) connects battery over its contact 6 and conductor 804 to the armature of busy relay ABO(7). There is a preference relay such as relay APO(7) and a busy relay such as relay ABO(7) for each of the auxiliary senders and the busy relays are arranged in a chain circuit so that any group relay may operate the rst preference relay associated with an idle auxiliary sender.

VThe preference circuit closed by each group relay enters the chain at a different point. `For example,` group relay .G9(.9) connects battery over its contact 6 and conduetor 901 to the armature of busy relay AB9(7). If the auxiliary' sender associated with relay ABO(7) is busy, relay ABO(7) will be operated and the .circuit above traced to conductor 804 will extend over a front contact of relay ABO(7) to the armature of some other busy relay. Assuming, however, that the rst auxiliary sender is idle, relay ABO(7) will not be operated and the circuit closed ,to vconductor 8.04 will extend over contract of relay ABO(7), contact 4 andwinding of relay APO(7) to ground. ARelay APO(7) operates in this circuit and 8 G0(8`), contact A'8 'of relay CST0(8), k'and conductor 80'0- to battery through the winding of hold magnet 1l-10(6). Select magnet 50(6) prepares all of th'e contact-s in the crossbar switch of Fig. 6 which are individual to the selected auxiliary sender. Hold magnet lH0(6) is indiviflual to the subscriber sender and lcloses crosspoint 607 completing the connection of the selected -auxiliary sender to the subscriber sender. in operating, opens the operating circuit for relay STO( S), but that relay is held operated temporarily in a locking circuit from battery over contact 10, winding and contact d of relay STO(8), contact l of relay G0(8), and contact 6 of relay STO(8) to conductor 502. `Hold magnet H0(6) also disconnects ground from conductor i 604 opening the locking circuit for relay G0(8) and the operating circuit for select magnet 80(6). As vsoon as the auxiliary sender is seized, ground is connected as will be described hereinafter, to conductor 1100 operating busy relay ABO'(7) to mark the auxiliary sender busy to the connector circuit. At its contact 6, relay ABO(7) opens the locking circuit for relay AP(6) causing that relay to release. Relay G0(8) releases, unless some other subscriber sender in the corresponding group is also Waiting for an auxiliary sender, in turn releasing relay STO(8) and restoring the connector control circuit to normal. Hold magnet H0(6) remains operated over its front contact and conductor 502 under the control of the subscriber sender. At its contact 2, hold magnet H0(6) connects ground to conductor 603 completing a circuit over Contact 4 of relay AS(5) to battery through the winding of relay SA(5) as a signal to the subscriber sender that the auxiliary sender has been attached.

Relay SA(5) operates and locks over its contact 6 and contact 8 of relay 7DG(5) to off-normal ground.

" With relay SA(5) operated a circuit is closed from ground, connected to conductor 201 by the roperated crosspoint of the units register as previously described,

contact 7 of relay SA(5), contact 5 of relay AS(5) to battery through the winding of relay SWF(5). Relay SWF(5) operates and inserts the auxiliary sender equipment in the fundamental circuit as will be traced hereinafter. It also makes certain adjustments in the PCI pulsing circuit to adapt it for pulsing to the auxiliary sender.

ln the meantime the subscriber sender has been receiving the eighth digit. When the eighth digit has operated the counting relays and the select magnets, hold magnet HMSTA(2) is not immediately operatedv but a circuit is closed from ground on the operating circuit of the select magnet, conductor 3427, back contact of relay SM3(2) to battery through the Winding of relay SM1(2). Relay SM1(2) operates and closes an obvious circuit through the left winding of relay SM2(2) causing that relay to operate. Relay SM2(2), in turn, operates relay SM3(2). Relay SM3(2) closes a circuit from ground over its front contact through the right winding of relay SM2(2) to the hold magnet sequence circuit 204, which for other digits extends as previously described, directly to the Winding of the associated hold magnet. For the present digit, the circuit extends over conductor 202, contact 9 of relay AS(5), contact 1 of relay 7DG(51), contact 5 and winding of relay DPT(5) to battery. Relay DPT(5) operates in this circuit and locks over its contact 6 through resistor 504 to ground. With relay DPT(5) operated, the circuit above traced to conductor 202 is extended over contact 4 of relay DPT(5) f and conductor 505 to battery through the winding of hold magnet HMSTAO). The hold magnet operates in this circuit and locks over a circuit not shown. When relay SM3(2) operated, it openedy the circuit of relay SM1(2) which in turn opened the circuit to the left winding of relay SM2(2), but relay SM2(2) was held operated in the circuitv by which relay DPT(5) was .operated. When the hold magnet HMSTA(2) locks', ground ou that circuit shunts the right winding of relay Hold magnet H0(6), 

